Bearings are typically press fit onto shafts by machines, making it difficult for a repair person to pull a worn bearing from its shaft.
Accordingly, inventors have developed numerous tools having utility as bearing pullers. Generally speaking, a bearing-engaging frame has an internally threaded aperture through which extends an elongate externally threaded screw member. The screw bears against the shaft that carries the bearing that is to be pulled so that rotation of the screw effects rearward travel of the frame and hence of the bearing due to the axial immobility of the shaft. There are many variations of this principal, with tools being adapted to fit differing shafts and bearings.
For example, the same principal applies where the shaft is axially movable. In that case, the frame that screw threadedly receives the shaft is stationary as the screw advances. The advancing screw bears against the movable shaft and the shaft recedes from the bearing. An example of this type of bearing puller, which is perhaps more accurately termed a bearing pusher, appears in U.S. Pat. No. 3,887,989 to Maynard.
Of course, many pullers do not remove bearings from shafts at all, but are used to pull apart items that are mounted on shafts in tight press fit relation thereto. In U.S. Pat. No. 3,182,385 to Esposito, the pole pieces of an automobile alternator are pulled apart from one another. A first pole piece is held against axial displacement by a cylindrical frame member, and an elongate screw member drives the shaft that carries both pole pieces away from the first pole piece to accomplish the separation.
In some puller devices, the elongate screw does not bear against the shaft. For example, in German patent no. 1078959 to Muller, a first frame is telescopically received by a second frame. The first frame has a leading end that bears against an immobile surface and the second frame has a leading end that engages the item to be pulled. A screw is screw threadedly received within an internally threaded aperture formed in the second frame and said screw's leading end bears against the first frame and not the shaft. Accordingly, rotation of the screw causes the second frame to retract with respect to the first frame, and said second frame carries the item to be pulled along with it.
Thus, the principals of mechanical extraction have been embodied in differing ways.
Certain automobiles, however, have alternators with a bearing and slip ring design that renders all of the known pullers useless, i.e., none of the known pullers have utility in connection with such designs. Thus, there is a need for a bearing puller having utility in connection with such alternator designs, but the prior art, taken as a whole, neither teaches nor suggests how an efficient puller for such bearings could be built.